The broadcaster John Simpson has spoken of his plans to take his own life should he be faced with serious illness in his later years, after participating in a documentary about the elderly in Britain.

"I'm not advocating [euthanasia] for anyone else. But just in my own case, I don't want my own six-year-old son to have his main memories of me as a gibbering, sad old freak," said Simpson, 67.

The BBC's world affairs editor was one of four celebrity pensioners who have examined the lives of older people in Britain as part of the When I'm 65 season, a series of programmes for prime-time BBC1 that broadcasts next week. "I'd rather take, in television terms, the early out, rather than to hang on purely for the sake of being alive and keeping on breathing and all the other functions," said Simpson.

For When I Get Older, the journalist joined Gloria Hunniford, 71, Tony Robinson, 65, and Lesley Joseph, 69, to live with elderly people in Britain dealing with the problems of isolation, poverty, grief and caring for an ill partner.

In the second episode of this unflinching look at old age, which will be broadcast on Wednesday and Thursday next week, the four move into a care home. "I don't think it's too over-dramatic to say that I think care homes, by and large, are prisons that people are sent to as a punishment for being old," said Robinson.

Hunniford, who said that moving into a care home filled her with "enormous dread", spoke about her sister, who died from dementia two years ago.

"What upset me more than anything was she went into a very good care home … but when push came to shove the nursing staff, though they were terrific, there weren't enough of them to make sure my sister ate and drank the fundamentals."

The documentary should prompt us all to think about how the elderly are treated in Britain, said the celebrity participants.

"In 100 years' time British people will look back on how we treated the elderly now with the same kind of disbelief and shock and horror that we look back on child labour," said Robinson. "I hope that this treatment of the elderly is a temporary aberration."

While better services and more state help are essential, the biggest lesson from the experience was that old people deserve more of our time and attention, said those who took part.

"I'm afraid in Britain we don't look after the elderly, the elderly don't have the place within the family," said Hunniford. "I do think that in some other countries the elderly do take their place at the head of the family and they are listened to. They have an opinion and they're not as invisible."

The When I'm 65 season also includes The Apprentice's Nick Hewer and Margaret Mountford examining work in your 70s in The Town That Never Retired; June Brown: Respect Your Elders, in which the Eastenders actor explores the lack of respect for the elderly in Britain; and How To Live Beyond 100, in which centenarians share their lives with the camera.

BBC1 controller Danny Cohen said: "[Care of the elderly] has implications for us now, but it also has huge implications for the future."